Fluid pressure device



. FLUID PRESSURE DEVICE Filed April 16', 1934 3 Sheets- Sheet 1 INVENTOR. MLL/s G. DOYLE ATTORNEYS Nov; 1, 1938. w, a DOYLE 2,134,780

FLUID PRESSURE DEVICE Filed A rii-ls, 1934 :5 SheetS-Sheet-Z ATTORNEYS Nov. 1, 1938. w, D YL 2,134,180

FLUID PRESSURIE. DEVICE Filed April 16, 1934 5 Sheets-Sheet 0 4 I //6 INVENTOR.

MLL/s G. DOYLE BY M] v ATTORNEY5 Patented Nov. 1, 1938 FLUID PRESSURE DEVICE Willis G. Doyle, Detroit, Mich. assignor to Hydraulic Brake Company, Detroit, Mich, a corporation 01' California.

, Application April 16, 1934, Serial No. 720,686 10 Claims. (Cl. 188-452) This invention relates to fluid pressure devices for actuating brakes.

In one embodiment of the invention the device is shown coupled to the compression element of a hydraulic brake system, and in another embodiment of the invention the device is shown c oupled to means for actuating a mechanical brake system.

The device includes a reservoir which under normal conditions is substantially full of fluid and a double diametral.cylinder supplied with fluid from the reservoir. The cylinder has therein two pistons yieldingly coupled together so that upon the initial movement of the compression stroke the pistons move at the same rate of travel until a predetermined pressure is reached, whereupon the rate of travel of one of the piste creases. drawn from the reservoir into the cylind ns de- Durlng the initial movement fluid is er between the pistons, and when .the predetermined pressure is reached a valve controlling the flow piston. This results in gradually stepping up the closes, of the other pressure in increments spread over a relatively wide range.

An object of the invention is to provide a fluid pressure device including means for gradually building up pressure.

Another object of the invention is to provide a fluid pressure device including means for stepping up pressure in increments spread over a relatively wide range.

A feature of the invention is a fluid pressure device having two pistons yieldingly connected and operable to vary the pressure.

Another feature of the invention is a fluid pressure device including a double diametral cylinder having therein pistons of different diameters yieldingly connected so that they may In different rates of travel to vary pressure.

Other objects and features of the invention will appear from the following-description taken in connection with the accompanying drawings which form a part or this specification, and in which- Figure 1 is a diagrammatical illustration of a motor vehicle brake system including a fluid presof the ntially Figure 4 is a longitudinal sectional view of a conventional fluid pressure device; and I Figure 5 is a diagrammatical illustration of the fluid pressure device connected to a mechanical brake system.

- 5 Referring to the drawings for more specific details of the invention, l0 represents a side rail of a motor vehicle chassis supporting a cross member it having secured thereto a housing or casing l4 including an open top reservoir i6. Bolted or otherwise secured to the top of the reservoir is a cover plate l8 having a filling open ing 20 ill Which is secured a closure plug 22 provided with a vent it.

A double diametral cylinder it is formed in the bottom of the reservoir. This cylinder has a port 28 providing communication between the cylinder I and the reservoir, and a portdtl also providing a communication between the cylinder and the reservoir, the port 30 being controlled by acheck valve 32, and secured in the reservoir above the ports 28 and 30 is a baflie plate M arranged to oppose agitation of the fluid in the reservoir and particularly in the viclnity'of the valves.

Fitted in the smaller chamber of the cylinder 7 2% is a reciprocatory piston 36 normally'seated on a washer Bl secured in position by a ring it seated in a circumferential groove in the wall of the cylinder. Formed in the back of the piston 36 is a recess 40 having seated therein one end of a push rod it, the other end of which has thereon a couplingdt connected by a boot dt to the cylinder for the exclusion of dust and other extraneous substances from the cylinder, and the coupling receives one end of a rod it the other end of which is pivotally connected to an operating lever Bil, preferably of the foot pedal lever type.-

The head of the piston at has thereon a concentric sleeve 5? and annular shoulders M and The sleeve communicates with a chamber 58 in the body of the piston. This chamber has a plurality of ports 60 providing communications between the chamber and a circumferential groove 62 in the piston, and a leak-proof cup 64 is fltted in the groove.

The larger chamber of the cylinder 26' has therein a reciprocatory piston 66. The body of this piston is reduced in cross-section to provide a chamber 68 between the piston and the wall of the cylinder. The head or the piston has a circumferential groove Ill and a plurality of ports 12 providing communications between the chamber 68 and the groove Ill, and .fltted in the groove is a collapsible leak-proof cup II. An annular rev cess 16 is formed in the head of the piston con centrically to an axial passage I8 having one or more grooves. This passage communicates with a chamber in the back of the piston, and the chamber 80 has a plurality of ports 82 providing communication between the chamber 80 and the chamber 68, and formed in the wall of the chamber 80 is a circumferential groove 84 having fitted therein a leak-proof cup 86.

The pistons 36 and 66 are connected by a rod 88 extending through the sleeve 62 and the passage I8. The rod is held against displacement by a diametral pin 80 in one end thereof and by a spider 92 secured to its other end. The rod carries a valve 04 for control of the passage I8, and a spring 96 interposed between the valve and the shoulder 56 urges the valve to its seat to close the passage I8.

A spring 98 of predetermined load has one end seated on the shoulder 64 and its other end seated in the annular recess I6. This spring tends to force the pistons 36 and 66 apart, and normally retains the valve 84 in open position. The chamber 80 has threaded therein a plug I00 provided with a recess I02 which receives one end of a connecting rod I04, the other end of which may be suitably connected to either the compression element of a hydraulic brake system or to a mechanical brake system.

A housing I06 is suitably secured to the housing I4 and provides a vent I0I for the right-hand end of the cylinder 26. The housing I4 includes an open top reservoir I08 having a cover plate IIO provided with a filling opening H2 in which is secured a plug II4 having a vent II6. A cylinder H8 formed in the bottom of the reservoir I08 has ports I20 and I22 providing communications between the cylinder and the reservoir.

This cylinder is arranged in axial alignment with the cylinder 26, and is provided with a port I24 communicating with a fluid pressure delivery pipe or conduit I26, which in turn communicates with branch pressure delivery pipes or conduits I28 and I80 communicating with motor cylinders I32 connected between the separable ends of friction elements I34 and I36 for spreading these elements into engagement with the drums I38 of brakes I40, and the friction elements of, the respective brakes are connected by retractor springs I42.

The cylinder I I8 has therein a valve I44 for control of the port I24 and a reciprocatory piston I46 retained in the cylinder by a washer I48 s ecured against displacement by a ring I60 seated in a circumferential groove in the wall of the cylinder. The piston has a recess I62 in its back for the reception of the rod I04 and the body of the piston is reduced in cross-section so as to provide a chamber I 66 back of the head of the piston, and fitted on the reduced portion at the base of the piston is a leak-proof cup I68. The head of the piston has a plurality of openings I60 controlled by a collapsible leak-proof cup I62 positioned on the head of the piston and held against displacement by a spring I64 interposed between the valve I44 and the cup I62.

Assuming that the apparatus is filled with fluid, upon depressing the foot pedal lever 60, force is applied through the rods 42 and 48 to move the piston 36 on its compression stroke. During the initial movement of the piston 36 on its compression stroke, the piston 66 is moved, due to the tension of spring 98, at the same rate of travel until a predetermined pressure is attained. During this movement fluid is drawn from the reservoir I6 through the ports 28 and 30 into the cylinder between the pistons. A portion of the fluid entering the cylinder through the port 28 passes through the chamber 68, the ports I2, and past the collapsible leak-proof cup I4 into the chamber between the pistons, and the remainder of the fluid entering the cylinder through the port 28 passes through the ports" into chamber 80, and from thence through the passage I8 and valve 64 into the chamber between the pistons.

Upon attaining the predetermined pressure,

the spring 88 is suillciently compressed to close on its compression stroke, fiuid in the cylinder H8 is displaced through the valve I44, port I24, fluid pressure delivery pipe or conduit I26 and branch fluid pressure delivery pipes or conduits I28 and I30 to the motor cylinders I32, resulting in spreading the frictional elements I34 and I36 into drum engagement.

Upon release of pressure on the foot pedal lever 50, this lever is returned to its normal position by a return spring 5| and upon the return of the foot pedal lever 50 to its normal position the applied force on the piston 36 is released. Upon release of the applied force on the piston 36, the piston I46 is returned to its retracted position by the spring I64, and since the piston I46 is connected by the rod I04 to the piston 66, which is connected to the piston 36, the pistons 36 and 66 are also returned to their retracted positions. As the pistons 36 and 66 return to their retracted position, fiuid is returned from cylinder 26 through the valve 94, passage I8, chamber 80, ports 82, and port 28 to the reservoir.

As the piston I46 returns to its retracted position, fiuid is returned from the motor cylinders I32 through the pressure delivery pipes or conduits I26, I28 and I30 and the valve I44 to the cylinder I I8. Because of the tension of the spring I64 and friction on the column of fiuid in the cylinder 8' and fiuid pressure delivery pipes I26, I28 and I30, the piston I46 is returned to its seat slightly in advance of the return of fluid from the motor cylinders, resulting in a partial vacuum in the cylinder II8, causing collapse of the leak-proof cup I62 resulting in drawlng fiuid from the reservoir I08 through the port I20, past the collapsible leak-proof cup I62 into the cylinder II8. When the cylinder has completely returned to its retracted position and its seat on the washer I48, the port I22 is uncovered, and upon further pressure in the cylinder II8 any excess fiuid in the cylinder H8 is returned to the reservoir through the port I22.

A modified form of the invention is illustrated in Figure 5. In this embodiment of the invention the connecting rod I04 has secured thereto a clevis 200 connected by a flexible boot 202 to the casing I4. The clevis is pivotally connected to a lever 206 secured to a shaft 208 having on its respective ends double end levers 2I0 connected by rods 2 I2 and 2 to the operative levers 2I6 of a conventional mechanical brake structure 2I8.'

The operation of this embodiment is substantially the same as in the preferred embodiment of the invention,- the only difference being that when force is applied through the connecting rod I04 the lever 206 is moved to rock the shaft 208. This movement of the shaft 208 moves the double end levers 2H) and exerts a pull on the rods in and 2 to movethe operative levers 2 l6 and thereby apply the brakes.

When the applied force is released the levers IIB are returned to inoperative position by retractor springs connected between the friction elements of the brakes M8. This movement of the levers M8 to inoperative position is transmitted to the levers 2W, resulting in rocking the shaft in reverse direction and moving the lever 206 through an angle, which movement is transmitted through the rod IM to the piston 66, and since this piston is connected to the piston 35, the pistonsBB and 66 are returned to their retracted positions.

While preferred embodiments of the invention have been described, it is to be understood that these are given merely as examples of underlying .principles of the invention, and since these may be incorporated in other specific structures it do not intend to be limited to those shown except as such limitations are clearly posed by the appended claims.

' Having thus described the various features of the invention, what I claim as new and desire to secure by Letters Patent is:

1. A fluid compression device comprising a reservoir, a pair of cylinders of difierent diameters, a piston in each of the cylinders, means for spac ing the pistons apart yieldable at a predetermined pressure, means for circulating fluid from the reservoir to the space between the pistons including a valve ior checking the flow of fluid,

means including a second valve for circulating fluid from the reservoir through one oi the pistons to the space between the pistons, one of said valves operable at a predetermined pressure to check the flow of the fluid through the piston, and means ior applying force to the pistons.

2. A fluid compression device comprising a fluid reservoir, a pair of cylinders of diderent diameters supplied therefrom, a piston in each oi the cylinders, a rod loosely connecting the pistons, a spring-pressed valve on the rod for control of a passage through one oi the pistons, a compression spring interposed between the pistons, a valve for control of a passage between the reservoir and the space between the pistons, an actuator for the pistons," a bralte system, and

linkage connecting the bre system to the pistons.

3. A fluid compression device comprising a huid reservoir, a pair of cylinders of dlderent diameters supplied therefrom, a piston movable in each of the cylinders, a rod connecting the pistons, said pistons being relatively movable on said rod, a spring-pressed valve on the rod ior control oi a passage through one oi the pistons, a compression spring interposed between the pistons, a valve for control oil a passage providing a communication between the reservoirandthe cylinders between the pistons, an actuator tor the pistons, a fluid pressure bralre system, and linkage connecting the bralre system to the pistons.

d. A fluid compression device comprising a pair oi pistons oi dlderent diameters arranged head to head and in spaced relation, a rod connecting the pistons and providing for relative movement thereof, a spring-pressed valve on the rod for control of a passage through one oi the pistons,

of pistons of different diameters arranged head to head and in spaced relation, a rod connecting the pistons and providing for relative movement thereof, a spring-pressed valve on the rod for control of a passage through one of the pistons, a leak-proof cup on the head of one of the pistons, a collapsible leak-proof cup on the head of the other piston controlling a plurality of passages through the head, and a compression spring interposed between the pistons.

6. A fluid compression device comprising a reservoir, a large diameter cylinder having a port providing communication between said large diameter cylinder and said reservoir, a check valve controlling said port, a small diameter cylinder concentric with the large diameter cylinder, a piston movable in each of said cylinders, a valve in the large diameter piston operable to close at a predetermined pressure, and means ior actuating the pistons operable to move the pistons at the same rate of travel during the initial movement thereof and thereafter to vary the rate oi travel of one of ti e pistons directly as the ratio of the piston areas.

"I. A fluid pressure device comprising a fluid reservoir, a large diameter cylinder having a port providing a communication between the reservoir and the cylinder, at checlr valve controlling the port, a small diameter cylinder-concentric with the large diameter cylinder, there being a second port connecting said large diameter cylinder with said reservoir, a piston in each oi the cylinders, the pistons being relatively movable, means for moving one of the pistons, means interposed between the pistons and adapted to impart simultaneous positive movement to the other piston during the initial movement of the piston, and thereiore to vary the movement oi one of the pistons directly as the ratio of areas of the pistons.

t. in a hydraulic bralre system of the class described, the combination of a reservoir, a pair oi? cylinders of different diameters supplied from said reservoir, a piston in each of the cylinders, means i'or supporting the pistons in spaced relapiston with the piston oi larger diameter, braking mechanism operated by said third piston, and a spring in said third cylinder for returning all pistons to their retracted positions.

9. In a bralre system oi the class described, the combination oi a reservoir, a pair oi cy1lnders pi difierent diameters supplied irom said reservoir, a piston in each oi the cylinders, means for supporting the pistons in spaced relationship between limits throughout their movement and yieldable at a predetermined pressure, means ior circulating fluid from the reservoir to the space between the pistons, means operable at a pro-determined pressure ior trapping the fluid between the pistons, means ior applying force to the pistons, bralring mechanism connected to the larger piston and operated thereby, and spring me i'or returning said mechanism and pistons to rest tlon.

ill

10. In a brake system of the class described,

the combination of a reservoir, a pair of cylinders or different diameters supplied from said reservoir, a piston in each of the cylinders, means for circulating fluid from the reservoir to the space between the pistons, means for supporting the pistons in spaced relationship between limits throughout their movement and operable at a predetermined pressure for trapping the fluid between the pistons, means for applying force to the pistons, braking mechanism operated by said pistons, and resilient means for returning 5 said mechanism and pistons to rest position.

WILLIS G. DOYLE. 

